El Windows Event Viewer It is one of the most powerful (and at the same time most unknown) tools incorporated into the Microsoft operating system for diagnosing and troubleshooting. Although many users overlook it, this viewer allows access to essential information about the status of your system, applications, and services, helping you identify the root cause of all kinds of errors. With a little practice and knowing what to look for, you can become a digital detective and find out why Windows or any installed program is failing.
Navigating through logs can seem overwhelming at first, but it's worth learning the keys to correctly interpreting the data and understanding how to use Event Viewer to detect errors, prevent problems, and improve your PC's performance. Here's a complete guide to everything you need to know, with tips, detailed steps, and explanations for each section of the viewer, including how to analyze Microsoft Defender errors and many practical tips to get the most out of this feature.
What is the Windows Event Viewer and what exactly is it for?
El Events viewer It is a tool included in all versions of Windows that shows detailed records of all relevant activities of the system, divided into categories such as Application, Security y System, among others. Its objective is to help you monitor, audit and troubleshoot Both everyday problems (hard shutdowns, freezes, unresponsive programs) and security incidents, unauthorized access attempts, or failures in key services. Thanks to its level of detail, it is the starting point for any advanced error analysis, whether for home users or system administrators.
How to access the Event Viewer in Windows step by step
- In recent versions of Windows, you can press Win + X and select Events viewer directly. You can also search for "eventvwr" from the start menu.
- If you have an older Windows, go to Control Panel > Administrative Tools > Event Viewer.
- If you're using the classic start screen, type eventvwr.msc, press enter and it will open.
Once inside, you will see a side panel where the Windows logs (Application, Security, System) and the tree Application and service logs. This contains both general and component-specific information, including ETW (Event Tracing for Windows) providers, which are very useful for advanced diagnostics.
Key Event Viewer Logs You Should Know About
- Application: This contains warnings, errors, and information generated by applications and services.
- Safety: It is key to detecting access, logins and suspicious activities.
- System: stores data about the operating system itself, drivers, hardware and internal services.
Furthermore, Application and service logs You'll find events related to individual components, such as Microsoft Defender, telemetry services, antivirus, or other critical modules. This is a must-see section if you're looking for the source of recurring errors or strange behavior in a specific utility.
How to Spot Errors and Warnings: Key Tips
In each record, events are classified by level: Information, Warning, Error y Critical. The ideal is to focus on those of type Error y Warning, especially if they coincide with the time you experienced the problem. Double-click any event to view expanded information in a window, including details, possible error codes, affected modules, and sometimes links or instructions for fixing the issue.
Tip: you can use the option Filter current record to display only errors or warnings, making it much easier to locate relevant faults.
Digging Deeper: Microsoft Defender Events and Common Diagnostics
Many users are looking for ways to interpret the messages generated by Microsoft Defender for Endpoint (also known as Sense or MDE) in Event Viewer. These messages offer valuable clues about the system's protection status and possible errors in onboarding, accessing the cloud, or communicating with external services.
Below is a breakdown of some of the most common error cases and codes you may encounter, along with their interpretation and recommendations:
- Starting and stopping the service: Messages stating that the service has been “started” or “shut down” usually indicate normal operation and do not require action.
- Error starting service: If you see messages like "Error starting Microsoft Defender for Endpoint service. Error code: ", it's a good idea to review other associated messages for causes. This could be due to issues with DLL files (MsSense), overloaded ETW sessions, insufficient permissions, or failing onboarding scripts.
- Server connection problems: Events like "could not connect to the server at " usually indicate network or proxy errors. Check the connectivity, firewall status and proxy settings.
- Failed or incomplete incorporation: Messages such as "Service not onboarded" or "No onboarding parameters found" indicate that the device is not properly linked to the management platform. Review the scripts and configuration packages and consider re-onboarding the device from scratch.
Troubleshooting common issues based on logged events
- Problems during onboarding/offboarding: When device integration with Microsoft Defender fails or is left unfinished, errors may appear related to changing the startup type, inability to clean up configurations, or saving settings. Redeploying scripts, verifying registry permissions, and restarting the device are often sufficient.
- Errors when applying cloud configurations: If an erroneous configuration file is received, the service will attempt to apply the last valid or default configuration. Monitor subsequent events to verify the restoration.
- ETW sessions saturated or not started: Session overload causes important events to go unrecorded. If the viewer consistently logs errors related to "lack of resources," restart your computer or close other monitoring sessions before trying again.
- Unable to update the record: If the events indicate that the GUID cannot be preserved, dependencies cannot be added, or keys (cryptographic keys, authentication status, etc.) cannot be updated, check that the user or service has write permissions in the Windows registry.
Interpretation of warnings and normal operation
Many of the messages collected in the Event Viewer are listed as «Notice of normal operation»; this indicates that the communication, startup, addition, or removal is proceeding correctly. However, it's always a good idea to review the details of each event if you notice abnormal behavior in the system or service.
On the other hand, some entries in the viewer refer to documentation or external resources for more information, such as guides on proxy configuration, onboarding scripts, or how to view specific Microsoft Defender logs. It's important to follow these recommendations and keep both the system and its components up to date.
Advanced tips for taking advantage of the Event Viewer
- Export relevant events: You can save any viewer entry as a .evtx file or in text format, making it easy to send to support or analyze on other computers.
- Use filtering and custom views: Create advanced filters to combine multiple criteria (e.g., error level and keywords) and detect patterns that would otherwise go unnoticed.
- Check the Event.log file: All events are stored in this file, which is useful for auditing or reviewing old logs in case the viewer encounters issues.
Common mistakes and how to address them by category
- Service startup errors: These issues typically involve DLL conflicts, missing dependencies, registry errors, or permission issues. If none of these solutions work, contact specialized support.
- Errors due to version incompatibility: Some events indicate attempts to apply packages or configurations for incompatible versions of Windows or Defender. Check that everything is up to date and compatible.
- Problems with telemetry or data upload: If the service is unable to send telemetry due to expired or invalid tokens, it will generally be temporary. The system will attempt to reactivate it once it has a valid token; otherwise, a service refresh or restart will be necessary.
Connectivity and network issues: key events
Some of the most common errors stem from an inability to connect to the cloud, servers, or authentication services. This can be due to misconfigured proxies, restrictive firewalls, internet outages, or expired packets. Events often offer clear clues with URLs, error codes, and explanatory messages. It's a good idea to check connectivity, adjust proxies, and ensure your firewall allows the necessary communication.
Notes on other uses of the Event Viewer and Supplementary Logs
El Viewfinder It is not only used for Microsoft Defender, but is also used for audit Any application that logs events in Windows. From FileMaker Server, network services, Windows updates, to drivers and hardware—they all generate logs here. Learning to interpret them and distinguish between information, warnings, and errors will allow you to act promptly and avoid major problems.
Some messages will direct you to alternative log locations (e.g., Event.log) or provide instructions on how to enable or disable specific logs based on the component or vendor. This will facilitate advanced troubleshooting or analysis after a serious issue.
Invest time in familiarizing yourself with the Windows Event Viewer This translates into faster diagnoses, less wasted time, and greater security for your computer. Mastering this tool will allow you to respond effectively to any error. Often, the messages may seem alarming, but they actually only report normal statuses or ongoing processes. If you detect recurring errors or are unable to resolve them by following the guidelines, don't hesitate to contact technical support, providing the details and exporting the viewer.